The present invention relates to soy products, and more particularly to stabilized soy beverages manufactured from dehulled-whole soybeans.
Soybean or legume based food products are known for their high protein content and other health benefits such as the reduction of blood cholesterol and incidents of osteoporosis. The manufacture of soy beverage products presents a variety of distinct problems due to the chemical composition of the soybeans. For example, typical whole soy beverages usually have a chalky, gritty, or fibrous texture due to the complex carbohydrates present in the soybean cotyledons and hulls. Further, soy beverages are typically plagued with a “beany” flavor caused by enzyme activity, in particular, lipoxygenase activity, that results from the cell tissue of soybean cotyledons being disrupted in the presence of moisture and oxygen.
In conventional soy beverage manufacturing processes, these problems have been addressed. Typical soymilk beverages include a combination of water and soymilk concentrate produced from a process whereby whole soybeans are dehulled and blanched. To reduce the chalky texture of the soy beverage, the soybeans are dry-dehulled prior to processing. Dry-dehulling is the industrial process whereby the soybeans are heated so that the hull is separated from the cotyledon. The soybean hull is then physically cracked and subsequently separated from the cotyledon. Alternatively, the chalky texture may be reduced by extracting the soybeans. Conventional extraction includes crushing the whole soybeans in water and pressing the resultant slurry to squeeze out a soybean liquid. To address the “beany” flavor of the resultant soy beverage, the soybeans are blanched—that is, boiled or steamed at very high temperatures. Blanching inactivates the lipoxygenase enzyme present in the soybean and eliminates the possibility of the soybean developing the “beany” flavor during subsequent processing. During the blanching step, however, the soy proteins are substantially denatured whereby solubilization of the soy proteins is inhibited.
Although manufacture of prior art soy beverages removes the chalky texture and “beany” flavor of the beverage, a distinct problem arises during storage of the beverage in containers. In particular, the beverage is extremely unstable. The beverage separates into at least two layers; a clumpy colloidal (particle) phase at the base of the container, and a free whey water phase at the top of the container. Accordingly, the beverage becomes unattractive in this separated, clumpy-looking state. Further, consumers must vigorously shake the container to recombine the colloidal phase and water phase before consuming the beverage to avoid an unpleasant texture. In the prior art, it was thought that the denaturation of the protein during the application of heat to inactivate the lipoxygenase was the cause of the colloidal separation.
To eliminate the unattractive appearance of prior art soy beverages, manufacturers conventionally package the beverage in opaque containers such as laminated paper boxes or colored plastic bottles. Although this conceals the separation of the colloidal phase and the water phase, the soy beverage still must be shaken to uniformly distribute the soybean particles in the water phase and prevent clumping when the beverage is poured from the storage container.
Manufacturers of soy beverages of the prior art have also addressed soy beverage instability by isolating soy nutraceuticals, such as particular soy proteins and soy isoflavones from whole soybeans, and putting the nutraceuticals alone in a beverage. Although the resultant soy beverage is somewhat stable, only a select few soy nutraceuticals are present therein. Thus, consumers obtain a limited number of soy nutraceuticals when they consume these soy beverages rather than the synergistic composition of all the soybean's nutraceuticals.